There is a substance in the human brain called dopamine, which can transmit information such as excitement and pleasure, so it is also called "happy substance". Drug is an exotic dopamine stimulant, which inhibits the formation and release of dopamine in human body, destroys the "ecological balance" in human body and forms the physiological and psychological dependence of human body. Only by increasing foreign "intake" can we maintain the physiological and psychological balance of the human body. After repeated times, the human body's tolerance to drugs is improved, and the role of drugs is gradually weakened. Drug addicts can only suppress their physical reactions with larger doses, and they get deeper and deeper. Once the external supply stops, the brain can't replenish dopamine for a while, and the body will fall into a crisis of supply and demand, which is the withdrawal reaction. Long-term use of morphine, sudden withdrawal, the body's suppressed dopamine secretion function will not immediately recover, so people will have various physiological symptoms caused by dopamine secretion disorder, such as runny nose and tears, dizziness, fatigue, drowsiness, and even discomfort and pain caused by eating bones.